Sir Galahad or KA Special

I've been doing a lot of sourdough as of late using the KA Bread flour obtained from my local supermarket. I'm well pleased with the results, and the oven spring is great.

I had the opportunity, and in my haste purchased several bags of the KA Sir Galahad flour before I realized I could have gotten the KA Special. I understand that the KA blue bag bread flour in my retail store is the same as the Special, commercial grade flour.

Now I'm wondering if this lower protein flour (SG) is going to be noticeable in the great oven spring I've been getting up to this point? Perhaps I could substitute 20% of Hi Trumps to my flour to regain any loss in oven spring that might occur? I've never had the good fortune of using the Sir Galahd flour, so I'm unsure of the degree of difference I should expect to see in my breads. Thank you